The Swedish national team star determined the final result with ten minutes left in regular time.
Rolfö stayed in front on a rebound, whereupon her shot was in turn blocked by a Real defender on the goal line.
But the 28-year-old didn't give up, stayed in front again and when Real wanted to clear, Rolfö was in the way and the ball took the Swede into the goal.
Dream start
Barça got off to a dream start to El Clásico when Ana-Maria Crnogorcevic made it 1-0 after just four minutes.
2–0 came at the end of the first, signed by Patri Guijarro, 3–0 at the beginning of the second by Aitana Bonmati before Rolfö punctuated the event.
Barcelona have won all eight games in the league so far and top the table five points ahead of runners-up Madrid CFF.
Real Madrid are fifth, eight points behind Barça but with a game less played.
Freja Olofsson remained on Real Madrid's bench for the entire match.
Rolfö stays at home
Next up is the national team break, where Sweden will face Australia away in a training international match on November 12.
Rolfö does not travel with the Swedish national team to the other side of the globe.
- I don't want to go into what it is about, but it is a decision that we have arrived at together, she said after the Champions League match against Rosengård at the end of October.